Array antennas, including but not limited to phased array antennas, are used in a wide variety of applications. In operation, the individual elements of the antenna are controlled to produce a desired beam pattern. For example, it is often desirable to produce a beam pattern having a main beam aligned in a direction of interest, while at the same time attenuating the sidelobes or beams in directions that are not of interest. This general configuration can increase the signal to noise ratio of the overall signal received by the antenna for a signal source aligned with the main beam.
Phased array antennas can be controlled to lower sidelobe levels or to place a null in the direction of jammers or other interfering signals. Almost all antenna array adaptive nulling algorithms require digital beamforming or a receiver at every element of the array in order to form a covariance matrix for calculating the adaptive weights. Digital beamforming is impractical for large arrays due to the cost of the required hardware and software systems. In addition, while there is some ability to attenuate the gain of an array antenna in areas outside of the main beam, sidelobes of various amplitudes will generally be present at various angles relative to the main beam. Therefore, selecting a beam pattern that produces nulls in areas of the beam pattern corresponding to interfering signal sources can be difficult.